This invention relates generally to containers for covering an inflatable restraint installation in a vehicle recess and, more particularly, to a container of unitary construction and to the method of manufacturing such a container.
Conventionally, the inflatable restraint, or air bag, provided for a vehicle driver is mounted in a receptacle located in the vehicle steering wheel assembly. It is conventional for the steering wheel hub to mount a container cover which incorporates a door formed in a decorative panel. This door is normally rectangular and is separable or separate from the surrounding panel area so that it can be swung open by the deploying air bag upon inflation.
Some of these cover doors comprise a three-sided cutout portion of the panel substrate covered by a foam padding and a decorative outer skin. The foam and skin include a tear seam line of weakened material along three sides of the door. This tear seam is fractured by the inflating air bag so that the door swings open about its fourth side, which functions as a hinge, to enable the cushion to properly deploy.
It is desirable for the outer skin or covering of the cover door match the material of the steering wheel for cosmetic conformity. Currently two methods of construction are used to make these cover doors. In one, a two-piece construction, a molded urethane covering, which matches the usual urethane steering wheel, is attached to a structural substrate, which includes a door swingable about a weakened hinge section.
In the other, a reinforcing mesh, or scrim, is molded into a urethane cover, and no substrate is used. Both constructions incorporate weakened sections in the urethane defining predetermined tear lines to create doors which tear open upon cushion deployment.
In the two-piece construction, each of the substrate and covering are separately made and thereafter assembled. The unitary construction eliminates one of the forming operations, plus the assembly operation. However, it has been found that it is difficult to assure that the reinforcing mesh is always properly located in the urethane cover, since it tends to "float" during the molding process. Also, a substantial layer of urethane and a substantial amount of reinforcing mesh must be used to prevent "sag" of the cover at elevated temperatures and to resist deformation upon incidental contact by the vehicle occupants.
A combination of both of these constructions is illustrated in U.S. Pat. No. 4,852,907 in which a partial structural substrate is embedded in a urethane covering. The substrate includes integral hinges, and the doors defined by predetermined tear lines in the urethane cover are reinforced by a nylon mesh. This construction suffers from the same floating mesh manufacturing problem described above and requires a complex molding operation to wed the substrate, the urethane and the mesh.
It is desirable to develop an inflatable restraint container construction which has a simplified construction which facilitates its manufacture.